Room temperature deformation behavior of multiphase Ni20at.%Al30at.%Fe and its constituent phases

Abstract

The microstructure of the multiphase alloy Ni20Al30Fe (where the composition is in approximate atomic per cent), processed through a casting and hot-extrusion route, consisted of a pro-eutectic β′ (ordered b.c.c. or B2-structured) phase in a fine (0.5 μm lamellae width) eutectic. The eutectic consisted of β′ + γ (f.c.c.) phases; the γ phase itself contained γ′ (ordered f.c.c. or L12-structured) precipitates. When tested in tension at room temperature, this alloy exhibited up to 20% elongation and a yield strength of up to 850 MPa. Crack stopping by the γ–γ′ phase was concluded to be an important factor contributing to the ductility of the alloy. In contrast, β′ Ni30Al20Fe, which had a composition similar to that of the pro-eutectic phase of the multiphase alloy, exhibited a similar yield stress of 800 MPa but only 2% elongation. This alloy deformed by «001å slip. Finally, the alloy Ni12Al40Fe, which was similar to the γ–γ′ phases of the multiphase alloy, exhibited 28% tensile elongation and a yield strength of 507 MPa and deformed by «110å slip.